Controlling the flow of light on chip: From photonic crystals to optical transistors

Leo Tom Varghese, Purdue University

Abstract

Optical transistors capable of forming an interconnected network are fundamental for optical information processing but have not been realized on a silicon chip. To be practical, an optical transistor must be cascadable, provide signal gain with logic level restoration, have input/output isolation and be free from critical biasing. It also needs to be compact and compatible with complementary metal-oxide-semiconductor (CMOS) technology. However, almost all previous proposals or demonstrations of optical transistors fail to meet these criteria. In this work, we demonstrate an all-silicon optical transistor using enhanced optical nonlinearity in two 5-micrometer-radius silicon rings which allows a small optical signal to control a large signal. While a single device can simultaneously achieve >3 dB signal gain and >20 dB ON/OFF ratio, a cascaded device, can yield a signal gain of >7 dB. An output ON/OFF ratio over 18 dB can be achieved with an input ON/OFF ratio of merely 2 dB. It also accomplishes fundamental logic operations like NAND or NOR on a single device, which normally require multiple electronic transistors. The optical transistor demonstrated here has many characteristics of its electronic analogue and promises to be a stepping stone for future optical computing. This work will also touch base on some of the early work on realizing inverse opal photonic crystals as an efficient thin film solar cell back-reflector and on fabricating photonic crystals through a scaffold of hydrogen silsesquioxane resist.

Degree

Ph.D.

Advisors

Qi, Purdue University.

Subject Area

Electrical engineering|Nanoscience|Optics

COinS